1. Field of the Invention
This invention relates to a component for illuminated sign cabinets. More specifically, the present invention relates to trim caps that are especially useful for channel letters.
2. Description of the Related Art
Backlit signs play an important role in modern commerce. A typical backlit sign is made up of a light box, often called a sign cabinet, which is covered by a light transmitting cover. The sign cabinet is typically a sheet metal enclosure containing light sources such as fluorescent tubes, incandescent lamps, or other illuminating devices. Light may also be brought to the sign cabinet from an external source by, for example, optical fibers or light pipes. The interior surface of the sign cabinet is often diffusely reflective, so as to improve light utilization and uniformity of illumination.
While many backlit signs are of simple rectangular or other geometric shapes, a particularly effective type of backlit sign is one which is made in the shape of an alphabetical letter, a number, a logo or other image, so that the entire sign becomes the image. A series of such signs can then be used, for example, to spell words or to collectively portray a larger image. Backlit signs of this sort are called channel letters, even though they often represent images other than letters.
Channel letters can be made by first fabricating a sign cabinet in the shape of the desired letter or other image. A light transmitting front cover is then fabricated from a sheet of light transmitting material such as polymethyl methacrylate or polycarbonate by cutting the sheet into the shape of the desired letter or other image. A flange-like border or retainer, commonly called a trim cap, is then attached to the peripheral edge of the cut out sheet. The trim cap serves to connect the cut out sheet to the sign cabinet and also to help block the entry of rain and other moisture into the inner chamber of the sign cabinet.
Trim caps are often fabricated from a length of trim cap stock material which can be purchased in bulk rolls. The trim cap material is formed around the cut out sign face by bending it at appropriate locations and mechanically or adhesively fastening it to the edge of the face. The completed cover is then fitted onto the front of the sign cabinet, with the edge of the trim cap engaging the front edge of the cabinet, thereby locating the cover in alignment with the cabinet. The cover can then be fastened to the cabinet by, for example, self tapping screws running through areas of overlap between the trim cap and the cabinet.
In the past, it has been common practice to attach trim caps to sign faces by use of solvent based adhesives. As an example, the sign face was placed over a sheet of plywood such that the exterior side of the sign face is facing the plywood. Next, the trim cap was placed along the edge of the sign face and held in place by a fixture such as a closely-spaced series of nails hammered into the plywood. A solvent based adhesive was then applied to the joint between the trim cap and the sign face edge along the perimeter of the latter. After the adhesive has dried, a second adhesive was commonly applied to increase the strength of the joint. After the second adhesive had dried, the nails were removed from the plywood for enabling the cover to be connected to the sign cabinet when desired.
As can be appreciated, the use of nails or other type of fixturing in the practice described above is somewhat time consuming and occupies space in the workshop during the time that the adhesive is allowed to dry. Moreover, the use of certain solvent-based adhesives can increase the risk health problems in individuals associated with its handling and use. The solvent of certain adhesives can also damage some types of plastic materials, rendering them unusable for the tasks at hand.